Gordon Brown will today maintain his campaign for the introduction of a so-called Tobin tax on global financial transactions in the face of US opposition.

Buoyed by the decision of the head of the International Monetary Fund to drop his opposition to the tax, the prime minister will tell the Commonwealth heads of government meeting that he still supports the measure.

The tax should be among a series of options to avoid a repeat of last year's international banking crisis, he will tell the summit, which opens in Trinidad and Tobago today.

Brown faced embarrassment earlier this month when he proposed a Tobin tax at a meeting of G20 finance ministers in St Andrews and Tim Geithner, the US treasury secretary, dismissed the idea.

But Brown will today tell the Commonwealth meeting: "I've said if you're going to look at how we can protect the public from future banking problems, there are a number of things you can look at.

"You can look at an insurance scheme. You can look at the creation of resolution funds. You can look at asking banks to hold contingent capital.

"You can look at transactions or a global levy of some sort, where we are better protected against the failure of banks, and where there is a greater fairness in the operation of the financial system.

"You've got to look at this at a global level. I will be raising this with my Commonwealth partners."

Downing Street sources said the prime minister was still keen on the tax, but stressed that he was not wedded to the idea and was keen to test the water.

"The prime minister is not banging the table about the Tobin tax," one said.

Brown received a boost this week when Dominique Strauss-Kahn, the managing director of the IMF, abandoned his opposition to the tax and said he was prepared to examine the pros and cons.

"We have been asked by the G20 to look into financial sector taxes," Strauss-Kahn told the CBI conference.

"This is an interesting issue. Can the tax system help reduce excessive risk-taking in the financial sector? Can it be used to further the legitimate goals of fairness and equity in this area?

"There are a number of ways to think about this, and we will look at it from various angles and consider all proposals."

Strauss-Kahn, who changed stance in the face of strong lobbying from Britain, France and Germany, added that he would look at other measures for raising money from the financial sector.